i 



ACTION OP PLATINA AND MERCURY. 177 



in folution. This effeft makes it advantageous to ufe a greater and gr. fulph. of 



. , . 1 ui f "'^^j throws 



quantity of the folution oi mercury than is merely capable ot jown platina and 



drawing down the given quantity of platina along with itfelf mercury united. 



in the form of a metallic precipitate. When this precipitate is 



walhed and dried; it will be found to weigh much more than 



the original quantity of platina; and the augmentation of 



weigiit has no limit but thofe of the mercury and the green 



fulphate of iron employed. But even after nitric acid has been Part of the latter 

 , , 1 • • • 1 • • • JS defended from 



boiled tor a long time and in great quantities upon this precipi- nitric acid. 



tate, until it no longer ditTolves any part of it, there ftill re- 

 mains more undilTolved matter than the original weight of the 

 platina ufed in the experiment. By expofure to heat little Heat;id^>yeso|^^, 

 more is left in general than the oriiginal platina; and fome- 

 times even a diminution may be obferved ; for as the experi- 

 raent is not attended with uniform fuccefs, it does not always 

 happen that the whole of the platina is precipitated, but a 

 portion of it will fometimes relift the a6lion of the green ful- 

 phate of iron, even when fufficient mercury has been ufed. 

 Before the precipitate has been expofed to heat it is diflfolved The compound 

 more eafily than platina by nitro-muriatic acid ; and the folu- more foluble 

 tion when nearly in a neutral flate gives a copious metallic than plat, in n. 

 precipitate, (yet not equal to the quantity employed,) when gjyg^s'^much me- 

 boiled with a folution of green fulphate of iron, tal. precip. by 



Exper. 2. When a mixed folution of platina and mercury is ^ " ? ' ° ^^' 

 precipitated by metallic iron, a quantity equal to the fum of the Exp. z. Me- 

 former metals is generally obtained. After nitric acid has been taH'ciron throws 

 1 -iir 1- 1 • r r down the pi. and 



boiled for a long time upon the precipitate fo formed, the mere, from a 



ori^rinal weight of platina, together with a confiderable in- "^i^^d folution. 



r • u u • J •. • -J r ri-i .• • -n Nitric acid does 



create, remains behind, nor can nitric acid lenubly diminith not deprive thi% 



it., It yields more eafily than platina to the adion of nitro-n^etal of all its 

 muriatic acid, and its folution in that acid, when neutralized, more"folluble in 

 gives a precipitate, as in the former experiment, by green n. m. acid j 

 fulphate of iron. If this precipitate be expofed to a firong ^^Y"^^"Pq„]^ 

 ^eat after it has been boiled with nitric acid, it lofes a great Heat ufually ex- 

 part of its weight, and the platina alone will generally be P^^^ '^^j^. "^"^"""^ 

 found to remain. 



Exper. 3. When a quantity of.ammoniacal muriate of platina ^^P* 3* Amal- 

 8 treated according to the method of Count Muffin Pullikin ^(531. munor* 



form an amalgam, and, after being rubbed for a confiderable plat.) ftrongly 

 me with mercury, is expofed in a crucible to a heat gradually ^l^ll^^ iaedoa 

 ncreafed till it becomes violent, a metallic powder remains in by n. m aci<^. 

 Vol. XI.— July, 1S05. N t^^ and copioudy 



